超低比转速离心泵非定常流动压力脉动特性研究

Study on Pressure Pulsation Characteristics of Unsteady Flow Field in Very-low Specific Speed Centrifugal Pump

超低比转速离心泵内部非定常流场导致的压力脉动问题是影响其安全稳定运行的重要因素。本文研究了“S”型叶片超低比转速离心泵内压力脉动的分布特征及其对安全稳定运行的改善效果,采用SST k-ω湍流模型,对“S”型叶片和直叶片两种形式分别进行定常以及非定常数值模拟,得到泵内叶轮叶片及隔舌处的压力脉动特征,并进行时域及频域分析。结果表明:直叶片小流量工况下压力脉动幅值最小,而“S”型叶片在额定工况压力脉动幅值最小;两种叶轮均以叶片通过频率为主,低频特征明显。“S”型叶片叶轮在0.6Qd(Qd为设计流量)、0.8Qd、1.0Qd、1.2Qd四种工况下叶轮出口及隔舌处监测点压力脉动幅值均有不同程度的下降,下降幅度达23%~47%,说明与直叶片相比,采用“S”型叶片能有效降低超低比转速离心泵的压力脉动幅值,提高超低比转速离心泵运行稳定性。

The pressure pulsation problem caused by the unsteady flow field in the very-low specific speed centrifugal pump is an important factor affecting its safe and stable operation. In this paper, the distribution characteristics of pressure pulsation in the very-low specific speed centrifugal pump with “S” type blades and its improvement effect on safe and stable operation, the SST k-ω turbulence model is used in this paper, the steady and unsteady numerical simulations of the “S” type blades and the straight blades are carried out respectively to obtain the characteristics of the pressure pulsation at the impeller and the cut water of the pump. The results show that the amplitude of pressure pulsation is smaller in the condition of straight blade with small flow rate, and smaller in the condition of “S” type blades with rated flow rate. The pressure pulsation amplitudes at the monitoring points at the impeller outlet and the cut water of the “S” type impeller under the four working conditions of 0.6Qd, 0.8Qd, 1.0Qd, 1.2Qdwere all decreased in different degrees, and the decrease range is 23%~47%, the “S” type blades can effectively reduce the pressure pulsation amplitude of the very-low specific speed centrifugal pump and improve the stability of the very-low specific speed centrifugal pump.